OP0039 TOWARDS UNDERSTANDING THE FAVORABLE EFFECT OF INCREASED BMI ON RADIOGRAPHIC PROGRESSION: A LARGE MRI-STUDY IN AN EARLY ARTHRITIS INCEPTION COHORT
Authors: N. Den Hollander, A. Van der Helm – van Mil, H. W. Van Steenbergen
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> Obesity is considered a risk factor for RA-development. Paradoxically, in RA obesity is associated with less severe radiographic progression. A previous MRI-study suggested that obesity associated with less osteitis and synovitis. <h3>Objectives</h3> To increase our understanding of the favorable association between obesity and radiographic progression, we performed a large MRI-study and aimed to 1) validate the association between BMI and MRI-detected osteitis/synovitis, 2) study whether this is a subgroup-effect in ACPA-positive/-negative RA or a general effect in early arthritides (also in 'non-RA diagnoses') and 3) study whether increased BMI associates with MRI-detected erosive progression, since MRI-detected erosive progression may follow osteitis but precedes radiographic progression. <h3>Methods</h3> We studied 1,029 patients (454 RA, 575 other arthritides), consecutively included in the Leiden Early Arthritis Clinic. At baseline, clinical parameters(including BMI) were measured and patients underwent hand-and-foot MRI that were RAMRIS-scored. 149 RA-patients underwent follow-up MRIs. Associations between baseline BMI and MRI-detected osteitis/synovitis, and baseline BMI and MRI-detected erosive progression were assessed using linear-regression and Poisson mixed-models. <h3>Results</h3> In RA, higher BMI associated with less osteitis(β=0.95; 95%CI=0.93-0.97) but not with synovitis, validating the previously found association with osteitis. The association of BMI with less osteitis was present in ACPA-positive RA(β=0.93; 95%CI=0.91-0.96), ACPA-negative RA(β=0.96; 95%CI=0.94-0.98) and other arthritides(β=0.98; 95%CI=0.96-0.996). During 2-years follow-up overweight and obese RA-patients had less MRI-detected erosive progression than normal-weight RA-patients(IRR=0.989, p-value=0.02 and IRR=0.989, p-value=0.03 respectively). This indicates that the MRI-detected erosive progression was 0.989 times lower per month or 23% lower over 2 years (IRR for one month 0.989, thus 0.989^24=0.77 over 2 years), in both overweight and obese patients, compared to normal weight patients (Figure 1A). Comparable results were found in both ACPA-positive and negative RA (Figure 1B and 1C). <h3>Conclusion</h3> High BMI associated with less osteitis at disease-onset; this was present in all early arthritis patients and not confined to ACPA-positive RA. Moreover, overweight/obesity in RA associated with less severe MRI-detected erosive progression over time. These findings substantiate the previously reported observation of less severe radiographic progression in obese RA-patients and bring us a step forward in unraveling the contradictory association between high BMI and less erosive disease, which is essential in a time where overweight and obesity keep increasing. <h3>REFERENCES:</h3> NIL. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.